In a typical cellular radio communication system (wireless communication system), an area is divided geographically into a number of cell sites, each defined by a radio frequency (RF) radiation pattern from a respective base transceiver station (BTS) antenna. The base station antennae in the cells are in turn coupled to a base station controller (BSC), which is then coupled to a telecommunications switch or gateway, such as a mobile switching center (MSC) and/or a packet data serving node (PDSN) for instance. The switch or gateway may then be coupled with a transport network, such as the PSTN or a packet-switched network (e.g., the Internet). The gateway is typically coupled with a packet-switched network using a data line such as a T1 cable or a fiber-optic cable.
When a mobile station (such as a cellular telephone, pager, or appropriately equipped portable computer, for instance) is positioned in a cell, the mobile station communicates via an RF air interface with the BTS antenna of the cell. Consequently, a communication path is established between the mobile station and the transport network, via the air interface, the BTS, the BSC and the switch or gateway.
To help manage call and data traffic in a wireless network, most cells are usually divided geographically into a number of sectors, each defined respectively by radiation patterns from directional antenna components of the respective BTS, or by respective BTS antennae. These sectors (which can be visualized ideally as pie pieces) can be referred to as “physical sectors,” since they are physical areas of a cell site. Therefore, at any given instant, an access terminal in a wireless network will typically be positioned in a given physical sector and will be able to communicate with the transport network via the BTS serving that physical sector.
Each sector may have allocated to it a distinct set of downlink channels that the BTS uses for transmitting signals to mobile stations and a distinct set of uplink channels that mobile stations may use for transmitting signals to the BTS. The uplink and downlink channels may use different carrier frequencies. Wireless telecommunications networks increasingly use multiple frequencies in some or all of their sectors in order to provide additional wireless capacity to those sectors. In particular, a sector may have allocated to it a plurality of uplink carrier frequencies, and a plurality of corresponding downlink carrier frequencies. As a result, the wireless coverage area is divided into a plurality of distinct “sector-carriers.” Each sector-carrier is associated with a particular cell or sector, and with a particular set of one or more carrier frequencies. For example, a sector-carrier may have a set of uplink channels that use a particular uplink carrier frequency and a set of downlink channels that use a particular downlink carrier frequency.
Under some communications protocols, such as 1xEV-DO, data transmitted on the forward link (from the BTS to the mobile station) of each sector-carrier is defined in terms of frames. These frames are divided into a number of time slots, each slot being approximately 1.667 ms in length. In addition, service providers may monitor the number of slots being utilized (the slot-utilization rate) at a given time or over a period of time for each sector-carrier. If the slot-utilization is at or near 100%, the service provider may install an additional sector-carrier, or attempt to optimize the BTS.
The explosive growth in demand for wireless data services, along with the emergence of high-speed communication protocols, has caused the level of data traffic in most cell sites to increase dramatically over recent years. As such, cellular service providers typically monitor portions of the wireless communication network infrastructure to determine whether an upgrade to the infrastructure is necessary. For example, the service provider may monitor the traffic on the data lines between the packet switched network and the wireless communication system. If the traffic is near or at the data lines' maximum throughput, the service provider may install an additional data line.
However, even though the slot-utilization rate or the amount of traffic on the data lines may approach 100% at certain times, it does not necessarily mean that an infrastructure upgrade (which can cost hundreds of thousands, if not millions, of dollars) is necessary. For example, data traffic within the wireless communication network may increase due to significant news events or sporting events. It is also possible that an increase in data traffic is due to another phenomenon. As such, wireless service providers often will not upgrade the wireless network's infrastructure until customers regularly experience slow data communications due to the infrastructure being overwhelmed.